He drank milk several times a day. He feasted on steak several times a week. He spent his mornings and afternoons in the wide-open countryside, grazing his 50 cows and dozens of goats on fine sprays of grass.

"I had everything," the 72-year-old said. "I was very rich."

That was before a drought crept across this region of western Somalia last year and again this year. Since then, the sorghum fields have dried up, the green grass has vanished and every last one of Ali's cattle has died, leaving him dependent on corn-soya rations.

By the end of the year, U.N. officials predict, nearly half of this nation's population, or about 3.5 million people, will need food aid, a dramatic spike driven by rampant political insecurity, skyrocketing global food prices, the devaluation of the local currency and a failure of nature's mercy, rain.

Those factors are also in play just across the border in Ethiopia, and aid groups are warning that large swaths of the Horn of Africa are hovering at the threshold of famine.

The signs are coming from all directions, especially near Somalia's capital, Mogadishu, where fighting between the Ethiopian-backed transitional government and Islamist insurgents has been heaviest. Along one road leading out of the city, more than 300,000 people have been living for more than a year under tarps and trees and with little access to food, and the situation is reaching a crisis point, according to the aid group Doctors Without Borders.

In recent months, aid workers have seen a 400 percent rise in the number of young children slipping through the stages of malnutrition: first becoming listless and withdrawn, their arms and legs growing thinner, their skin peeling off as it dies, and finally their bodies swelling, a condition caused by severe protein deficiency.

"Since May, the numbers have gone through the roof," said Susan Sandars, a spokeswoman for the group.

The situation here in the town of El Barde is repeated across central and southern Somalia, where most of the country's nearly 1 million displaced people have fled empty-handed; thousands more are arriving from Mogadishu every day. Though extended families have provided one safety net for the displaced, the traditional coping mechanism of sharing is reaching its limit.

Across the border in southern and eastern Ethiopia, the situation appears to be even worse: Numbers of severely malnourished children in some areas have increased sixfold in two months, according to the International Medical Corps, which runs screening centers there. At least 3.4 million Ethiopians are in immediate need of emergency food assistance.

The group's country director, Seifu Woldeamanuel, said that without additional intervention, children were "at grave risk of starvation."